sage.schemes:  Replace imports from sage.*.all for namespace packages

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Using `./sage -fiximports` from #34945.

Also remove trailing whitespace in the affected files.

Part of Meta-ticket #34201


CC:  @alexchandler100 @bhutz @yyyyx4

Component: **refactoring**

Author: **Alex Chandler, Matthias Koeppe**


_Issue created by migration from https://trac.sagemath.org/ticket/34951_

